Toronto Mayor Rob Ford has changed his mind and come out with a strong endorsement of Conservative Leader Stephen Harper ahead of Monday's federal election.

Less than a month ago Ford said he would stay out of the national campaign, except for his support of longtime family friend Jim Flaherty, who is seeking re-election for the Conservatives in the riding of Whitby-Oshawa.

The Toronto mayor was supposed to say a few words at a Conservative event in Brampton, Ont., on Friday night. It was expected that at that time he would add his support to the Harper campaign.

But on Friday afternoon Ford told CBC News he was making his support official.

"For the last 30 days I've watched the federal campaign very closely and I've decided to come out and support Stephen Harper. He's the only one that I feel that will be a benefit to the taxpayers of the city … Prime Minister Harper is holding the line on taxes and we need low taxes in the city to keep people living here and working here," Ford said in an interview in his office at Toronto City Hall.

The other parties "are going to cost the taxpayers a fortune," Ford said. "It's just tax, tax, tax and spend, spend, spend."

Although the Conservatives do not hold any ridings in the city of Toronto, Ford says he's optimistic that will change.

"I believe we will make a breakthrough," he said. "Electing Stephen Harper and the Conservative Party will benefit every taxpayer and resident of the city."

When asked what policies he endorsed Ford said the Conservative Party's commitment to building subways in Toronto was a major consideration.

"[P]eople want subways and we will have subways when Stephen Harper is the prime minister. And that's the bottom line."

Harper has spent very little time in Toronto during the six-week campaign. When he was asked about it on Friday morning, in Montreal, in advance of Ford's statement, Harper said he was "optimistic" about the party's chances.

"We are receiving very strong support from Toronto, and around Toronto, because this has been a government that's delivered for Toronto," Harper said.